Light and contrast

Most pond organisms are transparent. A little less light shows them better.

Living cells are mostly water, so in bright, even light they nearly disappear. Two simple fixes help.

Close the diaphragm

Close the aperture diaphragm under the stage (or lower the condenser) until edges and cilia stand out. Too far, and the image becomes grainy with dark rings; find the middle.

Simple dark field

At 40× and 100× you can make dark field with a disc of black card placed in the filter holder below the condenser, just large enough to block the direct light. The background turns black and organisms shine. It does not work at high power without a special condenser.